A new class of Epstein Barr Virus Nuclear Antigen (Class II) has been found which is more tightly bound to chromatin than the standard EBNA (Class I). This Class II EBNA has different antigenic and physicochemical properties than the Class I EBNA. Also, standard histones do not appear to react with these antisera. The Class II EBNA appears to be a modified histone or histone-like protein. It is planned to purify the Class II EBNA by the techniques described in the progress report, e.g., isoelectric focusing, molecular sieve and ion exchange chromatography, and preparative polyacrylamide gel electrophoresis. It is hoped to determine whether this antigen(s) is histone(s), whether it is modified by phosphorylation, acetylation, etc., or whether it is a histone-like protein. In the future it is planned to prepare antisera against this Class II EBNA.